WO2017154386A1 - Composite material containing layered double hydroxide, and battery - Google Patents

Abstract

A composite material containing a layered double hydroxide (LDH) is provided, the composite material including an LDH-containing functional layer formed on and/or in a porous base, the functional layer having significantly improved conductivity. The LDH-containing composite material of the present invention comprises a porous base and a functional layer disposed on and/or in the porous base, the functional layer comprising an LDH and a phase of another compound including Al, CO₃, and OH, the compound giving a peak at 2θ=9.8 to 10.3º when analyzed by X-ray diffractometry.

Description

Layered double hydroxide-containing composite material and battery

The present invention relates to a layered double hydroxide-containing composite material and a battery.

Layered double hydroxide represented by hydrotalcite (hereinafter also referred to as LDH) is a group of substances having anions that can be exchanged between hydroxide layers. It is used as a catalyst, an adsorbent, and a dispersant in a polymer for improving heat resistance. In particular, in recent years, it has been attracting attention as a material that conducts hydroxide ions, and addition to an electrolyte of an alkaline fuel cell or a catalyst layer of a zinc-air cell has also been studied.

When considering a catalyst, which is a conventional application field, a high specific surface area is necessary, so that synthesis and use in powdered LDH was sufficient. On the other hand, when considering application to an electrolyte utilizing hydroxide ion conductivity such as an alkaline fuel cell, a highly dense LDH film is desirable in order to prevent mixing of fuel gas and obtain sufficient electromotive force. It is.

Patent Documents 1 and 2 and Non-Patent Document 1 disclose an oriented LDH film. The oriented LDH film suspends the surface of a polymer base material horizontally in a solution containing urea and a metal salt to nucleate LDH. It is produced by forming and orientation growing. In each of the X-ray diffraction results of the oriented LDH thin films obtained in these documents, a strong peak of (003) plane is observed.

Chinese registered patent gazette CNC 1333113 International Publication No. 2006/050648

The present inventors have succeeded in manufacturing a dense bulk body of LDH (hereinafter referred to as an LDH dense body). In addition, while conducting evaluation of hydroxide ion conductivity for LDH dense bodies, it has been found that high conductivity is exhibited by conducting ions in the layer direction of LDH particles. However, when considering application of LDH as a solid electrolyte separator to an alkaline secondary battery such as a zinc-air battery or a nickel-zinc battery, there is a problem that the LDH dense body has high resistance. Therefore, for practical use of LDH, it is desired to reduce the resistance by thinning. In this regard, the oriented LDH film disclosed in Patent Documents 1 and 2 and Non-Patent Document 1 cannot be said to be sufficient in terms of orientation and density. Therefore, a highly densified LDH film, preferably an oriented LDH film is desired. In addition, considering the application of an LDH film as a solid electrolyte separator, the hydroxide ions in the electrolyte solution must move through the LDH film, so that the substrate supporting the LDH film is required to be porous. Is done.

In the LDH-containing functional layer such as an LDH film formed on and / or in the porous substrate, the present inventors include Al, CO ₃ and OH in the LDH-containing functional layer. It was found that the conductivity of the LDH-containing functional layer can be significantly improved by the presence of another compound phase.

Therefore, an object of the present invention is to provide an LDH-containing composite material in which the conductivity of the LDH-containing functional layer formed on and / or in the porous substrate is significantly improved.

According to one aspect of the invention, a porous substrate;
A peak is detected at 2θ = 9.8 to 10.3 ° when measured by the layered double hydroxide and X-ray diffraction method provided on and / or in the porous substrate. A functional layer comprising other compound phases comprising Al, CO ₃ and OH;
A layered double hydroxide-containing composite material is provided.

According to another aspect of the present invention, there is provided a battery including the layered double hydroxide-containing composite material as a separator.

It is a schematic cross section which shows one aspect | mode of the LDH containing composite material of this invention. It is a schematic cross section which shows the other one aspect | mode of the LDH containing composite material of this invention. It is a schematic diagram which shows a layered double hydroxide (LDH) plate-like particle. FIG. 3 is an exploded perspective view of a denseness discrimination measurement system used in the denseness determination test I of Examples 1 to 4. FIG. 3 is a schematic cross-sectional view of a denseness discrimination measurement system used in the denseness determination test I of Examples 1 to 4. FIG. 3 is an exploded perspective view of a measurement sealed container used in the denseness determination test II of Examples 1 to 4. FIG. 3 is a schematic cross-sectional view of a measurement system used in the denseness determination test II of Examples 1 to 4. It is a conceptual diagram which shows an example of a He transmittance | permeability measurement system. FIG. 6B is a schematic cross-sectional view of a sample holder used in the measurement system shown in FIG. 6A and its peripheral configuration. FIG. 5 is a schematic cross-sectional view showing an electrochemical measurement system used in Examples 1 to 4. It is the X-ray-diffraction result obtained in Example 1 (comparison) and Example 3. FIG. It is a SEM image which shows the surface microstructure of the composite material sample produced in Example 1 (comparison). It is a SEM image which shows the cross-sectional microstructure of the composite material sample produced in Example 1 (comparison). 6 is an SEM image showing a surface microstructure of a composite material sample produced in Example 3. 6 is an SEM image showing a cross-sectional microstructure of a composite material sample produced in Example 3.

Layered Double Hydroxide-Containing Composite Material The layered double hydroxide-containing composite material (LDH-containing composite material) of the present invention is formed on a porous substrate and on and / or in the porous substrate. Functional layers. The functional layer includes a layered double hydroxide (LDH) and another compound phase. The other compound phase is a compound phase containing Al, CO ₃ and OH whose peak is detected at 2θ = 9.8 to 10.3 ° when measured by the X-ray diffraction method. Thus, the conductivity of the LDH-containing functional layer can be significantly improved by the presence of another compound phase containing Al, CO ₃ and OH in the LDH-containing functional layer. As described above, for the practical application of LDH, a reduction in resistance by thinning is desired. However, according to the present invention, an LDH-containing composite material having an LDH-containing functional layer having a desirable low resistance can be provided. This is advantageous in applying LDH as a solid electrolyte separator to alkaline secondary batteries such as batteries and nickel zinc batteries.

Porous materials may be water permeable and breathable due to the presence of pores, but the functional layer is typically a dense layer and LDH to the extent that it does not have water permeability or air permeability (preferably both). It is preferable that it is densified. In this specification, “not having water permeability” means “measuring test I” adopted in the examples described later) or a measurement object when water permeability is evaluated by a technique or configuration equivalent thereto. It means that water that contacts one surface side (that is, the functional layer and / or the porous substrate) does not permeate the other surface side. In addition, “not breathable” means “denseness determination test II” employed in the examples described later) or a measurement object (that is, a functional layer) when the breathability is evaluated by a technique or configuration equivalent thereto. And / or porous substrate) means that bubbles caused by helium gas brought into contact with one surface side with a differential pressure of 0.5 atm are not generated in the water on the other surface side. The functional layer is preferably formed on a porous substrate. For example, as shown in FIG. 1, in the LDH-containing composite material 10, the functional layer 14 is preferably formed on the porous substrate 12 as an LDH dense film. In this case, needless to say, LDH may be formed on the surface of the porous substrate 12 and in the pores in the vicinity thereof as shown in FIG. 1 due to the nature of the porous substrate 12. Alternatively, as in the LDH composite material 10 ′ shown in FIG. 2, LDH is densely formed in the porous substrate 12 (for example, in the surface of the porous substrate 12 and in the pores in the vicinity thereof). At least a part of the substrate 12 may constitute the functional layer 14 ′. In this regard, the composite material 10 ′ shown in FIG. 2 has a structure in which the film-corresponding portion in the functional layer 14 of the composite material 10 shown in FIG. It suffices if the functional layer exists in parallel with the surface. In any case, in the LDH-containing composite material of the present invention, when the functional layer is densified with LDH to such an extent that it does not have water permeability and air permeability, it has hydroxide ion conductivity but water permeability and air permeability. It can have a unique function of not having.

As described above, in the LDH-containing composite material of the present invention, even though a porous base material that can have water permeability and air permeability is used, it does not have water permeability or air permeability (preferably both). It is preferable that a dense functional layer is formed. As a result, the LDH-containing composite material of the present invention as a whole has hydroxide ion conductivity but does not substantially pass an electrolytic solution such as an aqueous potassium hydroxide solution (that is, a substance other than hydroxide ions is substantially passed. And can function as a battery separator. As described above, when considering the application of LDH as a solid electrolyte separator for a battery, there was a problem that a bulk LDH dense body had high resistance, but in the composite material of the present invention, the porous substrate Since strength can be imparted, the LDH-containing functional layer can be thinned to reduce resistance. In addition, since the porous substrate can have water permeability, the electrolyte can reach the LDH-containing functional layer when used as a solid electrolyte separator for a battery. That is, the LDH-containing composite material of the present invention is extremely useful as a solid electrolyte separator applicable to various battery applications such as metal-air batteries (for example, zinc-air batteries) and other various zinc secondary batteries (for example, nickel-zinc batteries). Can be a material.

The porous base material in the composite material of the present invention is preferably capable of forming an LDH-containing functional layer on and / or in it, and the material and the porous structure are not particularly limited. Typically, the LDH-containing functional layer is formed on and / or in the porous substrate, but the LDH-containing functional layer is formed on the nonporous substrate, and then nonporous by various known methods. The porous substrate may be made porous. In any case, it is preferable that the porous base material has a porous structure having water permeability in that the electrolyte solution can reach the functional layer when incorporated in the battery as a battery separator.

The porous substrate is preferably composed of at least one selected from the group consisting of ceramic materials, metal materials, and polymer materials. More preferably, the porous substrate is made of a ceramic material. In this case, preferable examples of the ceramic material include alumina, zirconia, titania, magnesia, spinel, calcia, cordierite, zeolite, mullite, ferrite, zinc oxide, silicon carbide, and any combination thereof, and more preferable. Is alumina, zirconia, titania, and any combination thereof, particularly preferably alumina, zirconia (for example, yttria stabilized zirconia (YSZ), and combinations thereof). When these porous ceramics are used, it becomes dense. It is easy to form an excellent LDH-containing functional layer.Preferable examples of the metal material include aluminum and zinc, and preferable examples of the polymer material include polystyrene, polyethersulfone, polypropylene, epoxy resin, polyphenylene sulfide. Id, hydrophilized fluororesin.: None (quartet fluorinated resin such as PTFE) and any combinations thereof above-described various preferred materials are those having alkali resistance as a resistance against the electrolyte of the battery.

The porous substrate preferably has an average pore diameter of 0.001 to 1.5 μm, more preferably 0.001 to 1.25 μm, still more preferably 0.001 to 1.0 μm, and particularly preferably 0.001. 0.75 μm, most preferably 0.001 to 0.5 μm. By being within these ranges, it is possible to form an LDH-containing functional layer that is so dense that it does not have water permeability, while ensuring the desired water permeability and strength as a support for the porous substrate. In the present invention, the average pore diameter can be measured by measuring the longest distance of the pores based on the electron microscope image of the surface of the porous substrate. The magnification of the electron microscope image used for this measurement is 20000 times or more, and all obtained pore diameters are arranged in the order of size, and the upper 15 points and the lower 15 points from the average value. The average pore size can be obtained by calculating the average value of minutes. For the length measurement, a length measurement function of SEM software, image analysis software (for example, Photoshop, manufactured by Adobe) or the like can be used.

The surface of the porous substrate preferably has a porosity of 10 to 60%, more preferably 15 to 55%, still more preferably 20 to 50%. By being within these ranges, it is possible to form an LDH-containing functional layer that is so dense that it does not have water permeability, while ensuring the desired water permeability and strength as a support for the porous substrate. Here, the porosity of the surface of the porous substrate is adopted because it is easy to measure the porosity using the image processing described below, and the porosity of the surface of the porous substrate. This is because it can be said that it generally represents the porosity inside the porous substrate. That is, if the surface of the porous substrate is dense, the inside of the porous substrate can be said to be dense as well. In the present invention, the porosity of the surface of the porous substrate can be measured as follows by a technique using image processing. That is, 1) An electron microscope (SEM) image of the surface of the porous substrate (acquisition of 10,000 times or more) is obtained, and 2) a grayscale SEM image is read using image analysis software such as Photoshop (manufactured by Adobe). 3) Create a black-and-white binary image by the procedure of [Image] → [Tonal Correction] → [Turn Tone], and 4) The value obtained by dividing the number of pixels occupied by the black part by the total number of pixels in the image Rate (%). The porosity measurement by this image processing is preferably performed for a 6 μm × 6 μm region on the surface of the porous substrate. In order to obtain a more objective index, three arbitrarily selected regions are used. It is more preferable to employ the average value of the obtained porosity.

The functional layer in the composite material of the present invention contains layered double hydroxide (LDH). As is generally known, LDH is composed of a plurality of hydroxide base layers and an intermediate layer interposed between the plurality of hydroxide base layers. The hydroxide base layer is mainly composed of metal elements (typically metal ions) and OH groups. The intermediate layer of LDH is composed of anions and H ₂ O. The anion is a monovalent or higher anion, preferably a monovalent or divalent ion. Preferably, the anion in LDH comprises OH ^- and / or CO ₃ ^2- . LDH has excellent ionic conductivity due to its inherent properties.

In general, LDH is M ²⁺ _1-x M ³⁺ _x (OH) ₂ A ⁿ⁻ _{x / n} · mH ₂ O (where M ²⁺ is a divalent cation and M ³⁺ is a trivalent cation). A ⁿ⁻ is an n-valent anion, n is an integer of 1 or more, x is 0.1 to 0.4, and m is 0 or more). It is known as a representative. In the above basic composition formula, M ²⁺ may be any divalent cation, and preferred examples include Mg ²⁺ , Ca ²⁺ and Zn ²⁺ , and more preferably Mg ²⁺ . M ³⁺ may be any trivalent cation, but preferred examples include Al ³⁺ or Cr ³⁺ , and more preferred is Al ³⁺ . A ^n- can be any anion, but preferred examples include OH ^- and CO ₃ ^2- . Accordingly, in the above basic ^{formula, M 2+} comprises ^{Mg 2+, M 3+} comprises ^{Al 3+, A n-is} OH ^- and / or _CO preferably contains ^{3 2-.} n is an integer of 1 or more, preferably 1 or 2. x is 0.1 to 0.4, preferably 0.2 to 0.35. m is an arbitrary number which means the number of moles of water, and is a real number of 0 or more, typically more than 0 or 1 or more. However, the above basic composition formula is merely a formula of “basic composition” that is typically exemplified with respect to LDH in general, and the constituent ions can be appropriately replaced. For example, it may be replaced with some or all of the M ³⁺ tetravalent or higher valency cations in the basic formula, in which case, the anion A coefficient of ^n-x / n in the general formula May be changed as appropriate.

The functional layer in the composite material of the present invention also contains other compound phases containing Al, CO ₃ and OH whose peak is detected at 2θ = 9.8 to 10.3 ° when measured by the X-ray diffraction method. Including. The other compound phase containing Al, CO ₃ and OH is specified as a compound in which a peak is detected at 2θ = 9.8 to 10.3 ° when measured by the X-ray diffraction method. When the peak is analyzed by the crystal phase identification software, it can be identified as Al ₅ (CO ₃ ) ₃ (OH) ₁₃ .zH ₂ O (wherein z is 0 or more), but Al ₅ (OH) ₁₃ (CO ₃ ) What can be identified as a chemical formula of 5H ₂ O and the like can also be regarded as other compound phases. In any case, it can be said that the compound whose peak is detected at 2θ = 9.8 to 10.3 ° is a compound phase containing Al, CO ₃ and OH. The various conditions of the X-ray diffraction method may be determined in accordance with various conditions shown in Evaluation 1 of Examples described later.

According to a preferred embodiment of the present invention, when the surface of the functional layer is measured by an X-ray diffraction method, the peak intensity I _LDH due to the layered complex oxide detected at 2θ = 11.6 to 11.8 ° is detected. The ratio of peak intensities I _A due to other compound phases detected at 2θ = 9.8 to 10.3 °, that is, the ratio I _A / I _LDH is 0.3 or more, preferably 0.4 or more More preferably, it is 0.4 to 7, and still more preferably 0.4 to 5. Within these ranges, the ionic conductivity of the functional layer is further improved. This ratio I _A / I _LDH can be changed by appropriately controlling the time until the porous substrate is introduced into the raw material aqueous solution when forming the functional layer in the composite material manufacturing method described later. .

The functional layer preferably further contains manganese (Mn) at the interface with the porous substrate and in the vicinity thereof. The conductivity is further improved by the inclusion of Mn. The presence form of manganese is not particularly limited as long as the presence of Mn can be confirmed by elemental analysis, but manganese oxide is preferable. Manganese oxide may be in any form of crystalline, amorphous, and combinations thereof, but in the case of crystalline, the oxidation number is 2 to 4 such as MnO, MnO ₂ , Mn ₃ O ₄ , Mn ₂ O _3, etc. The manganese oxide is preferably MnO ₂ or Mn ₂ O ₃ . In the case of amorphous manganese oxide, it is non-stoichiometric and the chemical formula cannot be uniquely specified, but it is preferably in a form according to an oxidation number of 2 to 4 (for example, about 4).

The functional layer is formed on the porous substrate and / or in the porous substrate, preferably on the porous substrate. For example, when the functional layer 14 is formed on the porous substrate 12 as shown in FIG. 1, the functional layer 14 is in the form of an LDH dense film, which is typically formed from LDH. Become. Further, when the functional layer 14 ′ is formed in the porous substrate 12 as shown in FIG. 2, the surface of the porous substrate 12 (typically the surface of the porous substrate 12 and the vicinity thereof). Since the LDH is densely formed in the pores), the functional layer 14 ′ is typically composed of at least a part of the porous substrate 12 and LDH. The composite material 10 ′ and the functional layer 14 ′ shown in FIG. 2 can be obtained by removing a portion corresponding to the film in the functional layer 14 from the composite material 10 shown in FIG. 1 by a known method such as polishing or cutting. .

The functional layer preferably has no water permeability. Moreover, it is preferable that a functional layer does not have air permeability. More preferably, the functional layer does not have water permeability and air permeability. For example, the functional layer does not allow water to pass through even if one side of the functional layer is contacted with water at 25 ° C. for one week. That is, the functional layer is preferably densified with LDH to such an extent that it does not have water permeability. However, when a defect having water permeability locally and / or accidentally exists in the functional film, water impermeableness can be improved by filling the defect with an appropriate repair agent (for example, epoxy resin) and repairing the defect. Such a repair agent need not necessarily have hydroxide ion conductivity.

The functional layer preferably has a He permeability per unit area of 10 cm / min · atm or less, more preferably 5.0 cm / min · atm or less, and still more preferably 1.0 cm / min · atm or less. It can be said that the functional layer having the He transmittance within such a range has extremely high density. Therefore, the functional layer having a He permeability of 10 cm / min · atm or less can prevent a high level of passage of substances other than hydroxide ions when applied as a separator in an alkaline secondary battery. For example, in the case of a zinc secondary battery, permeation of zinc ions or zincate ions in the electrolytic solution can be extremely effectively suppressed. In principle, it is considered that the growth of zinc dendrite can be effectively suppressed when the zinc ion or zincate ion permeation is remarkably suppressed, when used in a zinc secondary battery. The He permeability is measured through a process of supplying He gas to one surface of the functional layer and allowing the He gas to pass through the functional layer, and a process of calculating the He permeability and evaluating the density of the functional layer. The The He permeability is expressed by the following formula: F / (P × S), using the He gas permeation amount F per unit time, the differential pressure P applied to the functional layer when He gas permeates, and the membrane area S through which He gas permeates. Calculated by Thus, by evaluating the gas permeability using He gas, it is possible to evaluate the presence or absence of denseness at a very high level, and as a result, substances other than hydroxide ions (especially zinc dendrite growth can be performed). It is possible to effectively evaluate a high degree of denseness such that the zinc ion or zincate ion to be caused is not transmitted as much as possible (only a very small amount is transmitted). This is because the He gas has the smallest structural unit among a wide variety of atoms or molecules that can constitute the gas, and the reactivity is extremely low. That is, He forms He gas by a single He atom without forming a molecule. In this respect, since hydrogen gas is composed of H ₂ molecules, a single He atom is smaller as a gas constituent unit. In the first place, H ₂ gas is dangerous because it is a combustible gas. Then, by adopting the He gas permeability index defined by the above-described formula, objective evaluation regarding the denseness can be easily performed regardless of differences in various sample sizes and measurement conditions. In this way, it is possible to simply, safely and effectively evaluate whether or not the functional layer has a sufficiently high density suitable for a zinc secondary battery separator. The measurement of the He permeability can be preferably performed according to the procedure shown in Evaluation 5 of Examples described later.

The layered double hydroxide is composed of an aggregate of a plurality of plate-like particles (that is, LDH plate-like particles), and the plurality of plate-like particles have their plate surfaces perpendicular to the surface of the porous substrate (substrate surface). It is preferable that they are oriented in such a direction as to cross each other diagonally. As shown in FIG. 1, this embodiment is an embodiment that can be realized particularly preferably when the LDH-containing composite material 10 is formed on the porous substrate 12 as the functional layer 14 as an LDH dense film. As in the LDH composite material 10 ′ shown in FIG. 2, LDH is densely formed in the porous substrate 12 (typically in the surface of the porous substrate 12 and in the pores in the vicinity thereof). This can be realized even when at least a part of the substrate 12 forms the functional layer 14 '.

That is, the LDH crystal is known to have the form of a plate-like particle having a layered structure as shown in FIG. 3, but the vertical or oblique orientation is determined by the LDH-containing functional layer (for example, an LDH dense film). This is a very advantageous property for the user. This is because an oriented LDH-containing functional layer (eg, an oriented LDH dense film) has a hydroxide ion conductivity perpendicular to this in the direction in which the LDH plate-like particles are oriented (ie, in a direction parallel to the LDH layer). This is because there is a conductivity anisotropy that is much higher than the conductivity in the direction. In fact, the present inventors have found that in an LDH oriented bulk body, the conductivity (S / cm) in the orientation direction is an order of magnitude higher than the conductivity (S / cm) in the direction perpendicular to the orientation direction. It has gained. That is, the vertical or oblique orientation in the LDH-containing functional layer of the present invention indicates the conductivity anisotropy that the LDH oriented body can have in the layer thickness direction (that is, the direction perpendicular to the surface of the functional layer or porous substrate). As a result, the conductivity in the layer thickness direction can be maximized or significantly increased. In addition, since the LDH-containing functional layer has a layer form, lower resistance than that of the bulk form LDH can be realized. The LDH-containing functional layer having such an orientation is easy to conduct hydroxide ions in the layer thickness direction. In addition, since it is densified, it is extremely suitable for use in functional membranes such as battery separators (eg, hydroxide ion conductive separators for zinc-air batteries) where high conductivity in the layer thickness direction and denseness are desired. Suitable.

Particularly preferably, the LDH plate-like particles are highly oriented in the vertical direction in the LDH-containing functional layer (typically an LDH dense film). This high degree of orientation is confirmed by the fact that when the surface of the functional layer is measured by the X-ray diffraction method, the peak of the (003) plane is not substantially detected or smaller than the peak of the (012) plane. (However, when a porous substrate in which a diffraction peak is observed at the same position as the peak due to the (012) plane is used, the peak of the (012) plane due to the LDH plate-like particle is used. This is not the case). This characteristic peak characteristic indicates that the LDH plate-like particles constituting the functional layer are oriented in a direction perpendicular to the functional layer. Here, it is needless to say that the “vertical direction” in this specification includes not only a strict vertical direction but also a substantially vertical direction similar thereto. In other words, the (003) plane peak is known as the strongest peak observed when X-ray diffraction is performed on non-oriented LDH powder. In an oriented LDH-containing functional layer, LDH plate-like particles function. Due to the orientation in the direction perpendicular to the layer, the peak of the (003) plane is not substantially detected or is smaller than the peak of the (012) plane. This is because the c-axis direction (00l) plane (l is 3 and 6) to which the (003) plane belongs is a plane parallel to the layered structure of the LDH plate-like particles. On the other hand, when the layer is oriented in the vertical direction, the LDH layered structure also faces in the vertical direction. As a result, when the surface of the functional layer is measured by the X-ray diffraction method, This is because the peak does not appear or becomes difficult to appear. In particular, the (003) plane peak tends to be stronger than the (006) plane peak when it exists, so it can be said that it is easier to evaluate the presence of vertical orientation than the (006) plane peak. . Therefore, in the oriented LDH-containing functional layer, the (003) plane peak is substantially not detected or smaller than the (012) plane peak, suggesting a high degree of vertical orientation. It can be said that it is preferable. In this regard, the LDH alignment film disclosed in Patent Documents 1 and 2 and Non-Patent Document 1 is one in which the peak of the (003) plane is strongly detected, and is considered to be inferior in the vertical alignment, In addition, it seems that it does not have high density.

The functional layer preferably has a thickness of 100 μm or less, more preferably 75 μm or less, still more preferably 50 μm or less, particularly preferably 25 μm or less, and most preferably 5 μm or less. Such thinness can reduce the resistance of the functional layer. The functional layer is preferably formed as an LDH dense film on the porous substrate, and in this case, the thickness of the functional layer corresponds to the thickness of the LDH dense film. Further, when the functional layer is formed in the porous substrate, the thickness of the functional layer corresponds to the thickness of the composite layer composed of at least part of the porous substrate and LDH, and the functional layer is porous. When formed over and in the substrate, this corresponds to the total thickness of the LDH dense film and the composite layer. In any case, when the thickness is as described above, a desired low resistance suitable for practical use in battery applications and the like can be realized. The lower limit of the thickness of the LDH alignment film is not particularly limited because it varies depending on the application, but in order to ensure a certain degree of hardness desired as a functional film such as a separator, the thickness is preferably 1 μm or more. Preferably it is 2 micrometers or more.

Method for Producing Layered Double Hydroxide-Containing Composite Material The layered double hydroxide-containing composite material (LDH-containing composite material) may be produced by any method. Preferably, the LDH-containing composite material is (1) a porous substrate is prepared, (2) Mn is adhered to the porous substrate if desired, and (3) a certain time at high temperature without pressurizing the raw material aqueous solution. (4) The porous base material is immersed in the raw material aqueous solution, and maintained for a certain period of time at a high temperature without being pressurized to produce a functional layer on and / or in the porous base material. Can do.

(1) Preparation of porous substrate The porous substrate is as described above, and is preferably composed of at least one selected from the group consisting of ceramic materials, metal materials, and polymer materials. More preferably, the porous substrate is made of a ceramic material. In this case, preferable examples of the ceramic material include alumina, zirconia, titania, magnesia, spinel, calcia, cordierite, zeolite, mullite, ferrite, zinc oxide, silicon carbide, and any combination thereof, and more preferable. Is alumina, zirconia, titania, and any combination thereof, particularly preferably alumina and zirconia, most preferably alumina. When these porous ceramics are used, the density of the LDH-containing functional layer tends to be improved. When using a porous substrate made of a ceramic material, it is preferable to subject the porous substrate to ultrasonic cleaning, cleaning with ion exchange water, and the like.

As described above, the porous substrate is more preferably composed of a ceramic material. The porous substrate made of a ceramic material may be a commercially available product or may be prepared according to a known technique, and is not particularly limited. For example, ceramic powder (for example, zirconia powder, boehmite powder, titania powder, etc.), methylcellulose, and ion-exchanged water are kneaded at a desired blending ratio, the obtained kneaded product is subjected to extrusion molding, and the resulting molded body is obtained. A porous substrate made of a ceramic material can be prepared by drying at 70 to 200 ° C. for 10 to 40 hours and then firing at 900 to 1300 ° C. for 1 to 5 hours. The blending ratio of methylcellulose is preferably 1 to 20 parts by weight with respect to 100 parts by weight of the ceramic powder. Further, the mixing ratio of the ion exchange water is preferably 10 to 100 parts by weight with respect to 100 parts by weight of the ceramic powder.

On the other hand, when a polymer material is used, it is preferable to prepare a polymer substrate that can be sulfonated in terms of suitability for the subsequent manganese deposition step. It is desirable that the polymer substrate capable of being sulfonated has alkali resistance as resistance to the electrolyte solution of the battery. Such a sulfonateable polymer substrate is selected from the group consisting of polystyrene, polyethersulfone, polypropylene, epoxy resin, polyphenylene sulfide, and hydrophilic fluororesin (tetrafluorinated resin: PTFE, etc.). It is preferable to consist of at least one. In particular, the aromatic polymer base material is preferable in that it is easily sulfonated, and such an aromatic polymer base material is selected from the group consisting of polystyrene, polyethersulfone, epoxy resin, and polyphenylene sulfide, for example. Most preferably, it consists of polystyrene.

(2) Adhesion of manganese (Mn) If desired, Mn is attached to the porous substrate. The attachment of manganese (Mn) to the porous substrate may be carried out by any method, but is not particularly limited. (I) It is oxidized by applying a sol containing manganese oxide to the porous member or (ii) by heating. After applying a solution or sol containing a manganese compound capable of producing manganese, the manganese compound is oxidized and decomposed by heat treatment to produce manganese oxide. In this case, preferable examples of the manganese compound include manganese nitrate, manganese chloride, manganese carbonate, manganese sulfate and the like, and manganese nitrate is particularly preferable. Application of the sol containing manganese oxide or a manganese compound is preferably performed by spin coating because it can be applied very uniformly. The spin coating conditions are not particularly limited. For example, the spin coating may be performed at a rotational speed of 1000 to 10000 rpm for about 5 to 60 seconds. The oxidative decomposition of the manganese compound by heat treatment is preferably performed by heating at 150 to 1000 ° C. for 5 minutes to 5 hours. In any of the above (i) and (ii), the manganese oxide may be in any form of crystalline, amorphous and combinations thereof, but in the case of crystalline, MnO, MnO ₂ , Mn Manganese oxide having an oxidation number of 2 to 4 such as ₃ O ₄ and Mn ₂ O ₃ is preferable, and MnO ₂ or Mn ₂ O ₃ is more preferable. In the case of amorphous manganese oxide, it is non-stoichiometric and the chemical formula cannot be uniquely specified, but it is preferably in a form according to an oxidation number of 2 to 4 (for example, about 4).

(3) pH adjustment of raw material aqueous solution On the other hand, raw material aqueous solution is hold | maintained at high temperature for a fixed time. This high temperature holding is desirably performed without applying pressure. Therefore, although it is desirable to cover the reaction vessel in order to suppress the reduction of the raw material aqueous solution due to evaporation, the lid is preferably simply placed on the upper end of the reaction vessel without being pressurized. The high temperature holding is preferably performed at 60 to 150 ° C., more preferably 65 to 120 ° C., still more preferably 65 to 100 ° C., and particularly preferably 70 to 90 ° C. The raw material aqueous solution contains magnesium ions (Mg ²⁺ ) and aluminum ions (Al ³⁺ ) at a predetermined total concentration, and contains urea. Due to the presence of urea, ammonia is generated in the solution by utilizing hydrolysis of urea, so that the pH value rises, and the coexisting metal ions form hydroxides so that LDH fine particles are partially precipitated. Or is likely to precipitate. Therefore, the pH of the raw material aqueous solution can be adjusted by appropriately adjusting the high temperature holding time, thereby controlling the proportion of other compound phases (compound phases containing Al, CO ₃ and OH) that can be precipitated together with LDH. can do. Typically, the pH of the aqueous raw material solution having an initial pH of about 3 can be raised to around pH 7-8. Further, since the hydrolysis is accompanied by generation of carbon dioxide, the anion can bring about carbonate ion type LDH. The total concentration (Mg ²⁺ + Al ³⁺ ) of magnesium ions and aluminum ions contained in the raw material aqueous solution is preferably 0.20 to 0.40 mol / L, more preferably 0.22 to 0.38 mol / L, still more preferably The amount is 0.24 to 0.36 mol / L, particularly preferably 0.26 to 0.34 mol / L. When the concentration is within such a range, nucleation and crystal growth can proceed in a balanced manner, and an LDH-containing functional layer excellent not only in orientation but also in denseness can be obtained. That is, when the total concentration of magnesium ions and aluminum ions is low, crystal growth becomes dominant compared to nucleation, and the number of particles decreases and particle size increases. It is considered that the generation becomes dominant, the number of particles increases, and the particle size decreases.

Preferably, magnesium nitrate and aluminum nitrate are dissolved in the raw material aqueous solution, whereby the raw material aqueous solution contains nitrate ions in addition to magnesium ions and aluminum ions. In this case, the molar ratio of urea to nitrate ions (NO ₃ ⁻ ) (urea / NO ₃ ⁻ ) in the raw material aqueous solution is preferably 2 to 6, and more preferably 4 to 5.

(4) Formation of LDH-containing functional layer containing other compound phases In a raw material aqueous solution that has been maintained at a high temperature for a certain period of time (that is, pH-adjusted), the porous substrate is placed in a desired orientation (for example, horizontally or vertically). Immerse and hold at high temperature without pressure. It is desirable that this high temperature holding is also performed without applying pressure. Therefore, although it is desirable to cover the reaction vessel in order to suppress the reduction of the raw material aqueous solution due to evaporation, the lid is preferably simply placed on the upper end of the reaction vessel without being pressurized. Thus, a functional layer containing LDH and other compound phases is formed on and / or in the porous substrate. When the porous substrate is held horizontally, the porous substrate may be suspended, floated, or disposed so as to be in contact with the bottom of the container. For example, the porous substrate is suspended from the bottom of the container in the raw material aqueous solution. The material may be fixed. When the porous substrate is held vertically, a jig that can set the porous substrate vertically on the bottom of the container may be placed. In any case, the LDH is perpendicular to or close to the porous substrate (that is, the LDH plate-like particles are such that their plate surfaces intersect the surface (substrate surface) of the porous substrate perpendicularly or obliquely. It is preferable to adopt a configuration or arrangement in which the growth is performed in any direction.

The high temperature holding after immersion in the porous substrate is also preferably performed at 60 to 150 ° C., more preferably 65 to 120 ° C., further preferably 65 to 100 ° C., and particularly preferably 70 to 90 ° C. It is. The upper limit temperature may be selected so that the porous substrate (for example, the polymer substrate) is not deformed by heat. The high temperature holding time may be appropriately determined according to the target density and thickness of the LDH-containing functional layer. As described above, the coexisting metal ions form hydroxides in the raw material aqueous solution whose pH has been increased through the hydrolysis of urea, whereby LDH is converted into other compound phases (compound phases containing Al, CO ₃ and OH). ). Further, since carbon dioxide is generated in the hydrolysis, LDH in which the anion is carbonate ion type can be obtained.

After forming the functional layer, the porous substrate is preferably taken out from the container and washed with ion exchange water.

The LDH-containing functional layer in the LDH-containing composite material produced as described above is one in which LDH plate-like particles are highly densified and are oriented in the vertical direction advantageous for conduction. In particular, when an LDH-containing functional layer having sufficient gas tightness is used for a battery such as a zinc-air battery, an improvement in power generation performance can be expected, and two types of zinc-air batteries using an electrolytic solution that could not be applied conventionally are used. It is expected to be applied to new separators such as zinc dendrite progress barrier and carbon dioxide invasion separator, which is a big barrier for the next battery. Similarly, it is expected to be applied to a nickel-zinc battery in which the progress of zinc dendrite is a major barrier to practical use.

By the way, the LDH-containing functional layer obtained by the above production method can be formed on both surfaces of the porous substrate. For this reason, in order to make the LDH-containing composite material suitable for use as a separator, the LDH-containing functional layer on one side of the porous substrate is mechanically scraped after film formation, or on one side during film formation. It is desirable to take measures so that the LDH-containing functional layer cannot be formed.

The present invention will be described more specifically with reference to the following examples.

Hereinafter, an example in which a layered double hydroxide alignment film is produced on a porous substrate will be shown. In addition, the evaluation method of the film | membrane sample produced in the following examples was as follows.

Evaluation 1 : Identification of a film sample Using an X-ray diffractometer (RINT TTR III manufactured by Rigaku Corporation), a radiation source: Cu-Kα, a voltage: 50 kV, a current value: 300 mA, a measurement range: 5 to 70 °, An XRD profile is obtained by measuring the crystalline phase of the membrane sample. About the obtained XRD profile, JCPDS card NO. Identification was performed using diffraction peaks of layered double hydroxide (hydrotalcite compound), Al ₅ (CO ₃ ) ₃ (OH) ₁₃ · zH ₂ O described in 35-0964.

Evaluation 2 : Observation of microstructure The surface microstructure of the film sample was observed with a scanning electron microscope (SEM, JSM-6610LV, manufactured by JEOL) at an acceleration voltage of 10 to 20 kV. Moreover, after obtaining the cross-sectional polished surface of the film sample with an ion milling device (manufactured by Hitachi High-Technologies Corporation, IM4000), the microstructure of the cross-sectional polished surface was observed by SEM under the same conditions as the observation of the surface microstructure.

Evaluation 3 : Density judgment test I
In order to confirm that the membrane sample has a denseness that does not have water permeability, a denseness determination test was performed as follows. First, as shown in FIG. 4A, an opening 122a having a size of 0.5 cm × 0.5 cm square was provided at the center on the film sample side of the LDH-containing composite material sample 120 (one cut into 1 cm × 1 cm square). Silicon rubber 122 was bonded, and the resulting laminate was bonded between two acrylic containers 124 and 126. The bottom of the acrylic container 124 disposed on the silicon rubber 122 side is pulled out, whereby the silicon rubber 122 is bonded to the acrylic container 124 with the opening 122a open. On the other hand, the acrylic container 126 disposed on the porous substrate side of the composite material sample 120 has a bottom, and ion-exchanged water 128 is contained in the container 126. At this time, Al and / or Mg may be dissolved in the ion exchange water. That is, by assembling the components upside down after assembly, the constituent members are arranged so that the ion exchange water 128 is in contact with the porous substrate side of the composite material sample 120. After assembling these components, the total weight was measured. Needless to say, the container 126 has a closed vent hole (not shown) and is opened after being turned upside down. As shown in FIG. 4B, the assembly was placed upside down and held at 25 ° C. for 1 week, after which the total weight was measured again. At this time, when water droplets were attached to the inner side surface of the acrylic container 124, the water droplets were wiped off. Then, the density was determined by calculating the difference in the total weight before and after the test. Even after holding at 25 ° C. for 1 week, when no change was observed in the weight of the ion-exchanged water, it was determined that the membrane sample (that is, the functional membrane) was so dense that it had no water permeability. .

Evaluation 4 : Density determination test II
In order to confirm that the film sample has a denseness that does not have air permeability, a denseness determination test was performed as follows. First, as shown in FIGS. 5A and 5B, an acrylic container 130 without a lid and an alumina jig 132 having a shape and size that can function as a lid for the acrylic container 130 were prepared. The acrylic container 130 is formed with a gas supply port 130a for supplying gas therein. The alumina jig 132 is formed with an opening 132a having a diameter of 5 mm, and a depression 132b for placing a film sample is formed along the outer periphery of the opening 132a. An epoxy adhesive 134 was applied to the depression 132 b of the alumina jig 132, and the film sample 136 b side of the composite material sample 136 was placed in the depression 132 b and adhered to the alumina jig 132 in an air-tight and liquid-tight manner. Then, the alumina jig 132 to which the composite material sample 136 is bonded is adhered to the upper end of the acrylic container 130 in a gas-tight and liquid-tight manner using a silicone adhesive 138 so as to completely close the open portion of the acrylic container 130. A measurement sealed container 140 was obtained. The measurement sealed container 140 was placed in a water tank 142, and the gas supply port 130 a of the acrylic container 130 was connected to a pressure gauge 144 and a flow meter 146 so that helium gas could be supplied into the acrylic container 130. Water 143 was put into the water tank 142 and the measurement sealed container 140 was completely submerged. At this time, the inside of the measurement sealed container 140 is sufficiently airtight and liquid tight, and the membrane sample 136b side of the composite material sample 136 is exposed to the internal space of the measurement sealed container 140, while the composite material sample The porous substrate 136 a side of 136 is in contact with the water in the water tank 142. In this state, helium gas was introduced into the measurement sealed container 140 into the acrylic container 130 via the gas supply port 130a. The pressure gauge 144 and the flow meter 146 are controlled so that the differential pressure inside and outside the membrane sample 136a is 0.5 atm (that is, the pressure applied to the side in contact with the helium gas is 0.5 atm higher than the water pressure applied to the opposite side). Whether or not helium gas bubbles were generated in the water from the composite material sample 136 was observed. As a result, when the generation of bubbles due to helium gas was not observed, it was determined that the film sample 136b had a high density so as not to have air permeability.

Evaluation 5 : He permeation measurement A He permeation test was performed as follows to evaluate the denseness of the film sample from the viewpoint of He permeability. First, the He transmittance measurement system 310 shown in FIGS. 6A and 6B was constructed. In the He permeability measurement system 310, He gas from a gas cylinder filled with He gas is supplied to a sample holder 316 via a pressure gauge 312 and a flow meter 314 (digital flow meter), and the denseness held in the sample holder 316 is measured. The membrane 318 is configured to be transmitted through one surface from the other surface and discharged.

The sample holder 316 has a structure including a gas supply port 316a, a sealed space 316b, and a gas discharge port 316c, and was assembled as follows. First, an adhesive 322 was applied along the outer periphery of the dense film 318 and attached to a jig 324 (made of ABS resin) having an opening at the center. Support members 328a and 328b (made of PTFE) provided with gaskets made of butyl rubber as sealing members 326a and 326b at the upper and lower ends of the jig 324 and further provided with openings formed from flanges from the outside of the sealing members 326a and 326b. ). Thus, the sealed space 316b was defined by the dense film 318, the jig 324, the sealing member 326a, and the support member 328a. The dense film 318 is in the form of a composite material formed on the porous substrate 320, but the dense film 318 is disposed so that the dense film 318 side faces the gas supply port 316a. The support members 328a and 328b were firmly fastened to each other by fastening means 330 using screws so that He gas leakage did not occur from a portion other than the gas discharge port 316c. A gas supply pipe 334 was connected to the gas supply port 316 a of the sample holder 316 assembled in this way via a joint 332.

Next, He gas was supplied to the He permeability measurement system 310 through the gas supply pipe 334 and permeated through the dense film 318 held in the sample holder 316. At this time, the gas supply pressure and the flow rate were monitored by the pressure gauge 312 and the flow meter 314. After permeation of He gas for 1 to 30 minutes, the He permeability was calculated. The calculation of the He permeability is based on the permeation amount F (cm ³ / min) of He gas per unit time, the differential pressure P (atm) applied to the dense film during He gas permeation, and the membrane area S (cm ² ) and calculated by the formula of F / (P × S). The permeation amount F (cm ³ / min) of He gas was directly read from the flow meter 314. Further, as the differential pressure P, the gauge pressure read from the pressure gauge 312 was used. The He gas was supplied so that the differential pressure P was in the range of 0.05 to 0.90 atm.

Evaluation 6 : Measurement of conductivity The conductivity of the membrane sample in the electrolytic solution was measured as follows using an electrochemical measurement system shown in FIG. The composite material sample S (porous substrate with LDH film) was sandwiched from both sides by a 1 mm thick silicone packing 40 and incorporated into a PTFE flange type cell 42 having an inner diameter of 6 mm. As the electrode 46, a # 100 mesh nickel wire mesh was incorporated into the cell 42 in a cylindrical shape having a diameter of 6 mm so that the distance between the electrodes was 2.2 mm. As the electrolytic solution 44, a 6 M KOH aqueous solution was filled in the cell 42. Using an electrochemical measurement system (potentiometer / galvanostat-frequency response analyzer, Solartron 1287A type and 1255B type), the frequency range is 1 MHz to 0.1 Hz, the applied voltage is 10 mV, and the real axis intercept Was the resistance of the membrane sample (porous substrate with LDH membrane). The same measurement as described above was performed only on the porous substrate without the LDH film, and the resistance of only the porous substrate was also obtained. The difference between the resistance of the composite material sample S (porous substrate with LDH film) and the resistance of only the substrate was defined as the resistance of the LDH film. The conductivity was determined using the resistance of the LDH film and the film thickness and area of the LDH.

Example 1 (Comparison)
(1) Preparation of porous substrate 70 parts by weight of a dispersion medium (xylene: butanol = 1: 1) and binder (polyvinyl butyral: Sekisui Chemical) with respect to 100 parts by weight of alumina powder (AES-12, manufactured by Sumitomo Chemical Co., Ltd.) BM-2 manufactured by Kogyo Co., Ltd. 11.1 parts by weight, 5.5 parts by weight of a plasticizer (DOP: manufactured by Kurokin Kasei Co., Ltd.), and 2.9 parts by weight of a dispersant (Rheodor SP-O30 manufactured by Kao Corporation) The mixture was stirred and degassed by stirring under reduced pressure to obtain a slurry. The slurry was molded into a sheet shape on a PET film using a tape molding machine so that the film thickness after drying was 220 μm to obtain a sheet molded body. The obtained molded body was cut out to have a size of 2.0 cm × 2.0 cm × thickness 0.022 cm and fired at 1300 ° C. for 2 hours to obtain an alumina porous substrate.

For the obtained porous substrate, the porosity of the porous substrate surface was measured by a technique using image processing, and it was 40%. The porosity is measured by 1) observing the surface microstructure with an accelerating voltage of 10 to 20 kV using a scanning electron microscope (SEM, JSM-6610LV, manufactured by JEOL Co., Ltd.). SEM) image (magnification of 10,000 times or more) is obtained, 2) a grayscale SEM image is read using image analysis software such as Photoshop (manufactured by Adobe), etc. 3) [Image] → [Tone Correction] → [2 A monochrome binary image was created by the procedure of [gradation], and 4) the porosity (%) was obtained by dividing the number of pixels occupied by the black portion by the total number of pixels in the image. This porosity measurement was performed on a 6 μm × 6 μm region on the surface of the porous substrate.

Further, when the average pore diameter of the porous substrate was measured, it was 0.3 μm. In the present invention, the average pore diameter was measured by measuring the longest distance of the pores based on an electron microscope (SEM) image of the surface of the porous substrate. The magnification of the electron microscope (SEM) image used for this measurement is 20000 times, and all the obtained pore diameters are arranged in order of size, and the top 15 points and the bottom 15 points from the average value, and 30 points per visual field in total. The average value for two visual fields was calculated to obtain the average pore diameter. For length measurement, the length measurement function of SEM software was used.

The obtained porous substrate was ultrasonically cleaned in acetone for 5 minutes, ultrasonically cleaned in ethanol for 2 minutes, and then ultrasonically cleaned in ion-exchanged water for 1 minute.

(2) Manganese coat of porous substrate Ion exchange water was added to manganese nitrate hexahydrate to prepare a manganese nitrate aqueous solution having a concentration of 0.2% by weight. On the alumina porous substrate obtained in the above (1), 0.2 ml of manganese nitrate aqueous solution was applied by spin coating. This spin coating was performed at a rotation speed of 8000 rpm for 10 seconds. The substrate was allowed to stand on a hot plate at 200 ° C., and manganese nitrate was thermally decomposed into manganese oxide. The manganese oxide thus formed is in an amorphous form according to XRD analysis. In addition, it is said that the oxidation number of the amorphous manganese oxide obtained by oxidizing and decomposing manganese nitrate at low temperature as mentioned above is about 4 in general.

(3) As the manufacturing raw material of the raw aqueous solution, magnesium nitrate hexahydrate _{(Mg (NO 3) 2 ·} 6H 2 O, manufactured by Kanto Chemical Co., Inc.), aluminum nitrate nonahydrate (Al _{(NO 3)} 3 · 9H ₂ O, manufactured by Kanto Chemical Co., Ltd.) and urea ((NH ₂ ) ₂ CO, manufactured by Sigma-Aldrich) were prepared. Weigh magnesium nitrate hexahydrate and aluminum nitrate nonahydrate so that the cation ratio (Mg ²⁺ / Al ³⁺ ) is 2 and the total metal ion molar concentration (Mg ²⁺ + Al ³⁺ ) is 0.34 mol / L. In a beaker, ion exchange water was added to make a total volume of 75 ml. After stirring the obtained solution, urea weighed at a ratio of urea / NO ₃ ⁻ = 4 was added to the solution, and further stirred to obtain an aqueous raw material solution.

(4) Formation of LDH film A Teflon (registered trademark) sealed container (autoclave container, inner volume 100 ml, outer jacket made of stainless steel) was coated with the raw material aqueous solution prepared in (3) above and manganese oxide in (2) above. A porous substrate was encapsulated together. At this time, the base material was fixed by being floated from the bottom of a Teflon (registered trademark) sealed container, and placed horizontally so that the solution was in contact with both surfaces of the base material. Thereafter, the raw material aqueous solution was held at a water temperature of 80 ° C. for 72 hours (3 days) to form a layered double hydroxide alignment film (functional layer) on the surface of the substrate. After the elapse of a predetermined time, the substrate is taken out from the sealed container, washed with ion-exchanged water, dried at 70 ° C. for 10 hours, and a dense layer of layered double hydroxide (hereinafter referred to as LDH) (hereinafter referred to as a membrane sample) ) Was obtained on a substrate. The thickness of the obtained film sample was about 1.5 μm. Thus, a layered double hydroxide-containing composite material sample (hereinafter referred to as a composite material sample) was obtained. In addition, although the LDH film was formed on both surfaces of the porous substrate, the LDH film on one surface of the porous substrate was mechanically scraped to give the composite material a form as a separator.

(5) Evaluation Results Evaluations 1 to 6 were performed on the obtained LDH film samples. The results were as follows.
-Evaluation 1: From the XRD profile, it was identified that the film sample was LDH (hydrotalcite compound). A peak identified as a compound phase containing Al, CO ₃ and OH was not observed.
-Evaluation 2: It was confirmed that there was no exposed portion of the porous substrate, and the LDH film was uniformly formed over the entire surface of the porous substrate. SEM images of the surface microstructure and cross-sectional microstructure of the composite material sample are shown in FIGS. 9A and 9B, respectively.
-Evaluation 3: It was confirmed that the membrane sample has high density so as not to have water permeability.
-Evaluation 4: It was confirmed that the membrane sample has a high density so as not to have air permeability.
-Evaluation 5: The He permeability of the membrane sample was 0 cm ³ / min · atm.
-Evaluation 6: The conductivity of the film sample was 0.3 mS / cm.

Examples 2-4
A layered double hydroxide-containing composite material sample was produced in the same manner as in Example 1 except that the LDH film containing other compound phases was formed as follows.

(Formation of LDH film)
The raw material aqueous solution prepared in the above (3) was charged into a Teflon (registered trademark) container (autoclave container, inner volume 100 ml, outer jacket made of stainless steel). At this time, the lid of the stainless steel jacket was kept without being sealed so that the inside of the container was not pressurized. Thereafter, the raw material aqueous solution was held at a water temperature of 80 ° C. for 17 hours (Example 2), 15 hours (Example 3) or 13 hours (Example 4), and then porous coated with manganese oxide in the same manner as (2) of Example 1 above. The substrate was charged. The initial pH of the aqueous raw material solution was about 3, but as a result of holding at 80 ° C., the pH rose to a level of 7 to 8 when the porous substrate was introduced. The porous substrate was fixed by being floated from the bottom of a Teflon (registered trademark) container, and placed horizontally so that the solution was in contact with both surfaces of the substrate. After that, as before, to prevent the inside of the container from being pressurized, it is simply placed without sealing the cover of the stainless steel jacket and kept at a water temperature of 80 ° C. for a predetermined time to form a layered composite on the substrate surface. A composite film (functional layer) containing a hydroxide and another compound phase (including Al, CO ₃ and OH) was formed. The retention time of the raw material aqueous solution at a water temperature of 80 ° C. was such that the total of the retention time before loading the porous substrate and the retention time after loading the porous substrate was 72 hours (3 days). After a predetermined time has elapsed, the substrate is taken out of the container, washed with ion-exchanged water, and dried at 70 ° C. for 10 hours to obtain a dense film of layered double hydroxide (hereinafter referred to as a membrane sample) on the substrate. It was. The thickness of the obtained film sample was about 1.8 μm. Thus, a layered double hydroxide-containing composite material sample (hereinafter referred to as a composite material sample) was obtained. Although the layered double hydroxide was formed on both surfaces of the porous substrate, the layered double hydroxide on one surface of the porous substrate was mechanically scraped to give the composite material a form as a separator. It was.

Evaluations 1 to 6 were performed on the obtained LDH film samples. The results were as follows.
-Evaluation 1: The XRD profile shown in FIG. 8 was obtained. From this XRD profile, the film sample is a compound phase containing LDH (hydrotalcite compound) and Al, CO ₃ and OH (specifically, Al ₅ (CO ₃ ) ₃ (OH) ₁₃ · zH ₂ O (wherein , Z is greater than or equal to 0)). Further, 2θ = 9.8 to 10.10 with respect to the peak intensity I _LDH (see the peak indicated as LDH in the figure) due to the layered complex oxide detected at 2θ = 11.6 to 11.8 °. As shown in Table 1, the ratio of the peak intensity I _A (see the peak marked A in the figure) due to the other compound phase detected at 3 °, that is, the ratio I _A / I _LDH was calculated. Met.
-Evaluation 2: From the SEM image of the surface microstructure of the membrane sample, it is confirmed that there is no exposed portion of the porous substrate, and the LDH film is uniformly formed over the entire surface of the porous substrate. It was done. SEM images of the surface microstructure and the cross-sectional microstructure of the composite material sample produced in Example 3 are shown in FIGS. 10A and 10B, respectively.
-Evaluation 3: It was confirmed that the membrane sample has high density so as not to have water permeability.
-Evaluation 4: It was confirmed that the membrane sample has a high density so as not to have air permeability.
-Evaluation 5: The He permeability of the membrane sample was 0 cm ³ / min · atm.
-Evaluation 6: The ionic conductivity of the membrane sample was as shown in Table 1.

Claims (12)

1. A porous substrate;
   A peak is detected at 2θ = 9.8 to 10.3 ° when measured by the layered double hydroxide and X-ray diffraction method provided on and / or in the porous substrate. A functional layer comprising other compound phases comprising Al, CO ₃ and OH;
   A layered double hydroxide-containing composite material.
2. When the surface of the functional layer is measured by an X-ray diffraction method, 2θ = 9.8 to the peak intensity I _LDH caused by the layered composite oxide detected at 2θ = 11.6 to 11.8 °. 10.3 ratio of the peak intensity _{I a} due to the other compound phase which is detected °, ie, the ratio _I a _{/ I LDH} is 0.3 or more, layered double hydroxides contained according to claim 1 Composite material.
3. The layered double hydroxide is composed of an aggregate of a plurality of plate-like particles, and the plurality of plate-like particles are oriented so that their plate surfaces intersect perpendicularly or obliquely with the surface of the porous substrate. The layered double hydroxide-containing composite material according to claim 1 or 2, which is oriented.
4. The layered double hydroxide is M ²⁺ _1-x M ³⁺ _x (OH) ₂ A ⁿ⁻ _{x / n} · mH ₂ O (wherein M ²⁺ is a divalent cation and M ³⁺ is trivalent) A ⁿ⁻ is an n-valent anion, n is an integer of 1 or more, x is 0.1 to 0.4, and m is 0 or more). The layered double hydroxide-containing composite material according to any one of claims 1 to 3.
5. The layered double hydroxide-containing composite material according to any one of claims 1 to 4, wherein the functional layer is provided on the porous substrate.
6. The layered double hydroxide-containing composite material according to any one of claims 1 to 5, wherein the functional layer has a thickness of 100 µm or less.
7. The layered double hydroxide-containing composite material according to any one of claims 1 to 5, wherein the functional layer has a thickness of 50 µm or less.
8. The layered double hydroxide-containing composite material according to any one of claims 1 to 5, wherein the functional layer has a thickness of 5 µm or less.
9. The layered double hydroxide-containing composite material according to any one of claims 1 to 8, wherein the functional layer does not have water permeability.
10. The layered double hydroxide-containing composite material according to any one of claims 1 to 9, wherein the functional layer does not have air permeability.
11. The layered double hydroxide-containing composite material according to any one of claims 1 to 10, wherein the functional layer has a He permeability per unit area of 10 cm / min · atm or less.
12. A battery comprising the layered double hydroxide-containing composite material according to any one of claims 1 to 11 as a separator.
    
    

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